gh-79282: Fix inspect.findsource breaking on class frame objects

[orlnub123]

https://bugs.python.org/issue35101

• Issue: inspect.findsource breaks on class frame objects #79282

[tirkarthi]

class A and class C look very similar to me with a function above them. Any difference between the tests?

[orlnub123]

You're right. When I added extra_a it was to catch any problems with A and B. Reversing the order of them should fix it.

[tirkarthi]

Thanks for the clarification. I feel one more case with a class definition inside a function can be added but I don't know if it's repetitive and can wait for a core dev on the test. I checked out the PR locally and LGTM from me.

Attaching my test as a reference.

diff --git a/Lib/test/inspect_fodder.py b/Lib/test/inspect_fodder.py
index a55e40bf0d..60f46c53e7 100644
--- a/Lib/test/inspect_fodder.py
+++ b/Lib/test/inspect_fodder.py
@@ -101,3 +101,13 @@ class A:
     def func(self):
         pass
     fr = inspect.currentframe()
+
+# line 105
+def extra_d():
+
+    class D:
+        def func(self):
+            pass
+        fr = inspect.currentframe()
+
+    return D()
diff --git a/Lib/test/test_inspect.py b/Lib/test/test_inspect.py
index 90eebec611..9d1c764535 100644
--- a/Lib/test/test_inspect.py
+++ b/Lib/test/test_inspect.py
@@ -432,6 +432,7 @@ class TestRetrievingSourceCode(GetSourceBase):
         functions = inspect.getmembers(mod, inspect.isfunction)
         self.assertEqual(functions, [('eggs', mod.eggs),
                                      ('extra_c', mod.extra_c),
+                                     ('extra_d', mod.extra_d),
                                      ('lobbest', mod.lobbest),
                                      ('spam', mod.spam)])

@@ -583,6 +584,7 @@ class TestGettingSourceOfFrames(GetSourceBase):
         self.assertNotSourceEqual(mod.B.fr, 85, 86)
         self.assertSourceEqual(mod.C.fr, 87, 90)
         self.assertNotSourceEqual(mod.C.fr, 85, 86)
+        self.assertSourceEqual(mod.extra_d().fr, 108, 111)

 class TestDecorators(GetSourceBase):
     fodderModule = mod2

[tirkarthi]

Just noticed that inspect.findsource is not documented and the tests also use inspect.getsource though it uses findsource internally. Can this be changed to inspect.getsource? Also please use the below with markdown so that the text is linked to the function docs.

Fix :func:`inspect.getsource` incorrectly returning the line number of the first
function above any given class frame objects.

[orlnub123]

That might be a bit unfair since more functions than just getsource use it. getcomments and getsourcelines use it directly while getsource uses getsourcelines, using it indirectly. Would it be OK to mention all of them?

[tirkarthi]

The last two commits ef1e750 and e4e811d used getsource in the NEWS though findsource was fixed since I think findsource is not documented. I think we can wait for the reviewer on this 👍

[tirkarthi]

Just for reference there is an open issue to document functions like findsource : https://bugs.python.org/issue17972

[JelleZijlstra]

I'm sorry this patch lingered for so long! I think it's close to ready but have a few comments.

[JelleZijlstra]

What is the motivation for the assertNotSourceEqual tests? If it's equal to a range, surely you don't have to also test that it's unequal to another range?

[JelleZijlstra]

inspect.findsource remains undocumented now. I'd suggest simply saying that the patch fixes finding class object frames in the inspect module.

Suggested change

	Fix inspect.findsource incorrectly returning the line number of the first
	function above any given class frame objects.
	Fix bug where the :mod:`inspect` module failed to identify the
	correct source code for class object frames.

[github-actions]

This PR is stale because it has been open for 30 days with no activity.